Polymerization of ethylene with nickel or cobalt on activated carbon



Oct. 19, E. F. PETERS ET AL 2,692,261

POLYMERIZATION OF ETHYLENE WITH NICKEL 0R COBALT ON ACTIVATED CARBONFiled April 25. 1951 SEPARATOR 2| 23 is 29 REACTQR 2 sun-mes ETHYLENE g'9 lo I l2 l3 u I? I5 5l 3Q FRESH CATALYST GASOLINE a2 b SEPARATING 4EQUIPMENT I FILTER AID 54 so as so as CATALYST 4 .4 DEWAXING zone i asosnssmme REGENERATION 55 SLVENT I WAX PRODUCT SLURRY OF nEwAxso WAXSOLVENT GREASE: CATALYST INVENTORSZ. uoum HYDROOARBON EDWIN F. PETERSBERNARD EVERING BY. 6 v

ATTORNEY:

Patented Oct. 19, 1954 BOLYMERIZATION OF ETHYLENE WITH NICKEL OR COBALTON ACTIVATED CARBGN Edwin F. Petersand Bernard L. Evering, Chicago,

111., assignors to Standard Oil Company, Chicago, Ill., a corporation ofIndiana Application April .25, 1951, Serial No. 222,802

16 Claims. i

This invention relates to a process for the polymerization of ethyleneand, more particularly, to a process for converting ethylene insubstantial yields to normally solid, wax-like and/or tough, resinouspolymerization products. In one aspect, this invention is concerned witha process for converting ethylene into one or 'more relatively highmolecular weight hydrocarbon products including grease-like hydrocarbonmaterials of Vaseline-like consistency at normal temperatures,hydrocarbon products of hard, paraiiin wax-like character and tough,resinous chemically inert, high molecular weight polymers having theessential characteristics of the commercial polyethylene films havingaverage molecular weights in the range of about 10,000 to about 30,000ihis application is a continuation-in-part of our copending applicationSerial No. 158,571, filed April 27, 1950, now abandoned.

The conversion of ethylene to dimers and to normally liquid olefinsboiling within the gasoline boiling range, principally hexenes, in thepresence of active carbon-supported cobalt and nickel catalysts is wellknown (note for example, German Patent 559,736 and U. S. Patent2,380,358). However, the polymerization of ethylene to form normallysolid, relatively high molecular weight products boiling substantiallyabove the boiling range of gasoline, has heretofore, to our knowledge,been accomplished only through the subjection of ethylene to rather hightemperatures and extremely high pressures (at least 100 C. and at least15,000 p. s. i. g.), optionally in the presence of small proportions ofoxygen (as in the processes described in U. S. Patent 2,153,553 of E. W.Fawcett et a1. and 2,188,465 of M. W. Perrin et a1.) or to the action ofperoxide catalysts, usually at high temperatures and pressures.

One object of our invention is to provide a novel process for theconversion of ethylene in the presence of certain eighth group metalcatalysts. Another object of our invention is to provide a process forthe conversion of ethylene in the presence of nickel and/or cobaltcatalysts to produce substantial yields of normally sol-idpolymerization products. Another object of our invention is to provide aprocess for the conversion of ethylene in the presence of nickel and/orcobalt catalysts to produce substantial yields of hydrocarbon greases.Another object of our invention is to provide a process for theconversion of ethylene in the presence of nickel and/r cobalt catalyststo produce substantial yields of tough, resinous, thermoplastic highmolecular weight polymers. Still another object of our invention is toprovide a process for the conversion of ethylene to normally solidhydrocarbon products at moderate pressures and relatively lowtemperatures. Yet another object of our invention is to provide the artwith new synthetic hydrocarbon waxes and resins. These and other objectsof our invention will become apparent from the ensuing descriptionthereof.

We have discovered, unexpectedly, that ethylene can be convertedprincipally, even almost exclusively, to normally solid polymers bytreatment with a nickel, cobalt or mixed nickel-cobalt catalyst incertain hydrocarbon reaction media which are liquid under the reactionconditions. The catalytic metals are preferably supported upon anactivated carbon, such as an activated coconut or wood charcoal. As hasbeen indicated above, ethylene polymerizes in the absence of said liquidhydrocarbon reaction media upon contact with cobalt catalysts underotherwise similar operating conditions to yield principally butenes andhexenes. With nickel catalysts under similar operating conditionssomewhat larger amounts of normally solid ethylene polymers along withthe lower molecular weight olefin polymers are produced.

Briefly, a gas stream comprising essentially ethylene, substantiallyfree of catalyst poisons or ethylene polymerization inhibitors, isbrought in contact with an activated carbon-supported metal selectedfrom the class consisting of nickel, cobalt and nickel-cobalt mixturesat a temperature sufficient to induce ethylene polymerization, saidtemperature being between about 10" C. and'about 250 C. or 300 C'., at apolymerization pressure between about 50 and about 15,000 p. s. i. g. inthe presence of a liquid hydrocarbon reaction medium such as benzene,xylenes, noctane or the like, employing about 0.52 to about percent byweight of ethylene, calculated on the total weight of ethylene andliquid hydrocarbon reaction medium, at a weight space velocity selectedin the range of about 0.01 to about 5 grams of ethylene per hour pergrain of catalyst. Under these conditions, ethylene is converted, insubstantial, often predominant yields, to grease-like and normally solidpolymers having molecular weights between about 300 and 25,000 or evenmore, accompanied by relatively minor yields of ethylene dimer andliquid polymerization products boiling within the boil-'- ing range ofgasoline.

In the usual practice of the present invention, gaseous, liquid and someof the normally solid ethylene conversion products are continuouslywithdrawn from the reaction zone and may be separated by conventionalfractional distillation, filtration and crystallization procedures. Apart of the normally solid polymerization products may be retained uponthe surface of the solid polymerization catalyst.

In the present process, the catalysts do not appear to suffersubstantial, or sometimes even appreciable, loss of polymerizationcapacity by reason of the occlusion of solid ethylene polymerizationproducts thereon. However, from time to time the catalysts can bedewaxed (which term herein is intended also to include deresining byliquation of solid polymers there from and/or by extracting thecatalysts with Wax solvents at temperatures in the range of about 100 C.to about 300 C. or higher at atmospheric or superatmospheric pressures.For example, dewaxing can be effected by contacting the catalyst witharomatic hydrocarbon solvents such as benzene, toluene, xylenes,ethylbenzene, ethyltoluenes, misitylene, isodurene and the like, or withother solvents, following which the solution of wax in the extractionsolvent is separated from the catalyst, cooled to efiect crystallizationof wax and resins from the solvent and/or subjected to evaporation toremove the solvent from the solute. The dewaxed catalyst can then bereturned to the reaction zone for contact with further amounts ofethylene or can first be regenerated by treatments hereinafterdescribed. The normally solid ethylene polymerization products producedby our process can be fractionated by known techniques and by thespecific methods which will be described hereinafter.

To describe the present invention in somewhat greater detail, attentionwill be concentrated first upon the polymerization feed stock. The feedstock comprises essentially ethylene. Carbon monoxide, oxygen, hydrogensulfide and ammonia function as catalyst poisons and should be removedfrom feed stocks in which they are present. Although carbon monoxide isquite readily removed by treating the catalyst with hydrogen, we havefound that ammonia is very tenaciously adsorbed in the activatedcarbon-supported catalysts and is quite diflicult to remove by hightemperature (300-350" C.) hydrogen treating of the catalysts. Oxygen inrelatively small proportions, up to 1000 to 2000 p. p. m., does notappear to exert a deleterious effect on the present ethylenepolymerization process, although when the cumulative amount of oxygencharged to the catalyst is as high as about 3 mol percent based upon themetal content of the catalyst, substantial deactivation of the catalystmay occur. Commercial ethylene streams containing from about 100 toabout 1000 parts per million of oxygen can, therefore, be employedwithout special deoxygenation treatment in the practice of the presentinvention. In peroxide-catalyzed process for ethylene polymerization,amounts of oxygen within the range of 100 to 1000 p. p. m. in theethylene feed stock are usually considered to exert a substantialdeactivating effect.

The presence of acetylene in amounts substantially greater than tracequantities is undesirable. Thus (run 25) the treatment of a mixture of 2percent acetylene, 68 percent ethylene and 30 percent benzene with acatalyst consisting of 1 percent nickel supported on nitric acid-washedcoconut charcoal in a flow reactor at 155 C., 2200 p. s. i. g. and 0.5volume of total feed per hour per volume of catalyst failed to yieldmore than a trace of solid ethylene polymer, possibly because of theformation of nickel acetylide. Under otherwise identical conditions butin the absence of acetylene the polymerization of ethylene has beenfound to yield 60 grams of solid polymer in 5 hours.

Ethane and other normally gaseous parafiin hydrocarbons in the ethylenecharging stock function as diluents, but not as catalyst poisons andmay, therefore, be present in the feed stock. Normally gaseous olefinsother than ethylene are preferably removed from the feed stock sincethey tend to reduce the degree of ethylene polymerization, especiallywhen present in concentrations greater than about 10 volume percent,based on ethylene.

The olefin and liquid hydrocarbon reaction medium can be separatelyintroduced into contact with the catalyst. In another mode of operationa solution of the feed stock in the liquid hydrocarbon reaction mediumcan be prepared and the. solution brought into contact with the solidcatalyst. Thus, ethylene can be selectively absorbed from its mixtureswith other gases, particularly hydrogen, methane and ethane, in asuitable liquid hydrocarbon -meaction medium, preferably an aromatichydrocarbon such as benzene, a xylene, ethylbenzene, mesitylene or thelike at temperatures between about 10 C. and about 100 C. and pressuresbetween about 50 and about 1200 p. s. i. g., and the rich absorbent canbe brought into contact with the solid polymerization catalyst. Ifdesired, both the gaseous feed stock and the liquid hydrocarbonreaetionmedium can simultaneously be brought into contact with the solidcatalyst. a

The employment of a liquid hydrocarbon reaction medium as hereinafterdefined is essential to the operation of the present process in order toavoid the polymerization of ethylene principally to gaseous and lowboiling liquid ethylene polymers and to effect a shift in the productdistribution principally or, substantially exclusively, towards theformation of normally solid polymers from ethylene. The liquidhydrocarbon reaction medium employed in the present process appears toperform a variety of functions, and to perform these functions invarying degrees depending upon the operating conditions, catalyst andidentity of the medium. Thus, the liquid hydrocarbon reaction mediumappears to function as a solvent for ethylene to bring ethylene into thenecessary contact with the catalyst surface and/or growing ethylenepolymer chain. The liquid hydrocarbon reaction medium may function toprotect the growing polymer chain from chain breakers, such asreaction-inhibiting impurities in the feed stock, polymer already formedupon certain parts of the catalyst surface, etc. The liquid hydrocarbonreaction medium serves to reduce the viscosity of the solid'polymerretained upon and within the catalyst and thus may facilitate theprocess of transferring ethylene where it is needed. The

' medium dissolves some of the normally solid products. has not yieldedevidence of the presence of :more than trace amounts of aromatics in theproducts. It should be understood, however, that weare nowise bound bythe theoretical considerations herein advanced to explain possible modesof action of the liquid hydrocarbon reaction medium. The fact remainsthat the inclusion. of certain liquid hydrocarbon media in thepolymerization reaction zone in contact with the catalyst produces astartling, unpredictable,

and in alarge measure unexplained, change in the polymerization ofethylene conducive to the formation of high yields of normally solidhydrocarbon products.

Various classes of hydrocarbons which are liquid under thepolymerization reaction conditions of the. present process and which arenot aliphatic olefins can be employed. As the examples submittedhereinafter show, we have successfully employed hydrocarbonsrepresentative of the aromatic hydrocarbon series, particularly themononuclear aromatic hydrocarbons, viz. benzene, xylenes, mesitylene andxylene-p-cymene mixtures. Tetrahydronaphthalene has also been employed.In addition, we may employ such aromatic hydrocarbons as toluene,ethylbenzene, isopropylbenzene, n-propylbenzene, sec-butylbenzene,t-butylbenzene, ethyltoluene, ethylxylenes, lhemimellitene,pseudocumene, prehnitene, isodurene, diethylbenzenes, isoamylbenzene andthe like. Suitable aromatic hydrocarbon fractions can. be. obtained bythe selective extraction of aromatic naphthas, from hydroformingoperations, etc. The aromatic hydrocarbons may contain more or lesssaturated hydrocarbons, as commercially produced, but should be freed ofpolyolefins and aromatic olefins such as styrene before use in thepresent invention by acid treatment, L

e. g. with anhydrous p-toluenesulfonic acid, sulfuric acid, or byequivalent treatments, for example treatment with maleic anhydride. Ingeneral,,'both commercial availability and suitability for the presentpurpose indicate a preference for mononuclear aromatic hydrocarbonshaving between about 6 and about 10 to 12 carbon atoms per molecule.Alkylbenzenes, particularly methylbenzenes, constituted a preferredsubclass of liquid hydrocarbon reaction media for our purposes. We mayalso employ certain alkyl naphthalenes which are liquid under thepolymerization reaction conditions, for example, l-methylnaphthalene,2-methylnaphthalene, l-ethylnaphthalene, 2-ethylnaphthalene,2-isopropylnaphthalene, l-n-amylnaphthalene and the like.

Certain classes of saturated aliphatic hydrocarbons can also be employedas a liquid hydrocarbon reaction medium in the present process. Thus, wemay employ various saturated hydrocarbons (alkanes and cycloalkanes)which are '6 reaction mediaswhich can bev employed are f'notiii allsenses equivalent. to each other. Inicertain instances we have. notedthat. individual liquid hydrocarbon reaction media exert specificdes'lred effects to a high degree and that the efiects exerted by theparticular hydrocarbon in question are not general to all the liquidhydrocarbons which maybe employed as reaction media in the presentinvention. As will appear hereinafter,

we have discovered preferred effects attendant on the employment ofpolymethylbenzenes such as the xylenes, 'mesitylenes, and xyleneepcy'me'ne mixtures and the like as liquid hydrocarbon media, and these.media. therefore constitute a preferred subclass of liquid hydrocarbonreaction media for the practice of the present invention. The liquidhydrocarbon. reaction medium may be present in the polymerizationreaction zone in proportions of about 10 to about: 98- percent-byweight, based on the weight of both-ethylene and reaction medium. Theliquid hydrocarbon-reaction medium is present in thereaction zoneasadistinct liquid phase. At low ratios ofethylene to the hydrocarbonreaction medium, for example ratios between about 2 and about 30percent, temperature control during the course of the ethyleneconversion process can be readily accomplished owing to the presence inthe raction zone of a large liquid mass having relatively high heatcapacity. The liquid hydrocarbon reaction medium can, moreover, becooled by indirect heat exchange inside or outside the reaction zone.

At relatively high concentrations of ethylene in the hydrocarbonreaction medium, say between about 60 and about percent by weight, basedon both components, a. high rate of ethylene polymerization may beachieved even though complete solution of the ethylene in the reactionmedium may not prevail in the reaction zone and a product may beproduced directly from the reactor which contains a relatively lowproportion of the hydrocarbonv reaction medium. However, as will appearfrom the specific examples supplied hereinafter, the percentage of g theethylene charge which is converted at low concentration in a hydrocarbonreaction medium may be substantially higher than at a high ethyleneconcentration in the same reaction medium.

The catalysts employed in the operation of'our process compriseessentially nickel, cobalt and cobalt-nickel mixtures. We have foundthat nickel catalysts are surprisingly superior to co balt catalysts forthe purpose of producing tough, resinous high molecular weight polymersfrom ethylene.

In order to increase the accessibility of the catalytic metal to theethylene, it is desirable by some means to dilute, attenuate or extendthe catalytic metal, and this may be done in a variety of ways. Thus,the catalystic metal may be diluted by employing it in the form of, analloy with one or more other metals which do not adversely affect thedesired ethylene polymerization reaction; the catalytic metal anddiluent metal can both be deposited on active carbon, e. g., activatedcoconut charcoal. For example, the nickel and/or cobalt may be employedas alloys or mixtures with copper. The catalysts may be employed in theform of pellets, powders, turnings, screens or colloidal dispersions inthe-liquid hydrocarbon reaction medium. The surface of the catalyticmetal may be etched by treatment with strong acids, particularly nitricacid, followed by water washing and hydrogen reduction in order'toeffect activation.

Although it might appear obvious that the surface of the catalytic metalcould be readily and conveniently extended by deposition of the metalupon any one of a number of porous or absorbent supports, we have madethe surprising discovery that this is not, in general, feasible. Highlyactive nickel and cobalt catalysts for hydrogenation of fats and otherunsaturated organic materials have heretofore been prepared bydepositing various nickel and cobalt salts or other compounds uponporous supports such as silica gel, alumina, celite, kieselguhr,aluminosilicates, etc. decomposing the nickel or cobalt compound,usually to form the corresponding metal oxide and hydrogenation of themetal oxide to produce the catalytically active metal (Carleton Ellis,Hydrogenation of Organic Substances, D. Van Nostrand Co., Inc. (1930)).We have found, however, that the nature of the support specifically andunpredictably affects the utility of the nickel and cobalt catalysts forthe purposes of polymerizing ethylene to normally solid polymers.Alumina and silica supports greatly reduce or, in some instances,virtually destroy the power or nickel and cobalt to catalyze thepolymerization of ethylene to form normally solid polymers.

We have found that activated carbons, particularly activated charcoalsderived from cellulosic materials having surface areas between about 700and about 1200 m. /g., pore volumes of about 0.53 to 0.58 cc. per gramand pore diameters of about 20 to 30 A., and, in some instances, smallamounts of combined oxygen, greatly enhance the catalytic activity ofnickel and cobalt for the purposes of ethylene polymerizations, ascompared with the activity of the unattenuated catalytic metals. Whenactivated carbons are covered with water and the mixture is stirred forsome time at room temperature, the water leaches various materialstherefrom and its often happens that the resultant aqueous solutions areslightly basic; it is desirable to neutralize the basic materials insuch carbons, particularly coconut charcoals, by treating the carbonswith nitric acid, following which residual nitric acid is removed by theapplication of heat to eifect vaporization, or decomposition andvaporization. The nitric acid treatment of carbon causes some oxidationthereof.

The catalytic metal can be deposited upon the active carbon support byvarious methods well known in the art of catalyst preparation. Thus,

the catalytic metal can be adsorbed upon the carbon in the form of adecomposable salt, e. g., in the form of nickel or cobalt nitrates,formates, carbonates, etc. We prefer to prepare the catalysts fromnickel and/or cobalt nitrates. The adsorbed salt can be decomposed toyield nickel or cobalt oxides upon' and within the active carbonsupport, and the oxides can be reduced to the catalytically activemetals by treatment with hydrogen. The salt of the catalytic metal canbe adsorbed on the active carbon support in amounts suflicient toprovide reduced catalytically active metal in concentrations betweenabout .01 and about 20 percent by weight in the finished catalyst.Hydrogen reduction of the catalytic metal oxides can be effected attemperatures between about 175 C. and about 400 C. preferably from about200 C. to about 250 C. and hydrogen pressures from about 1 mm. ofmercury to about 2000 p. s. 'i. g.

To enter into some further detail concerning the step of decomposing themetal salt, e. g.,

nickel nitrate, to produce the corresponding metal oxide in theabove-described procedure for producing catalysts, we may state thatmetal salt decomposition is suitably practiced under a. partial vacuumsuch as l-20 mm. of mercury (absolute pressure) or, preferably, in thepresence of steam. 7

As an alternative to adsorbing the catalytic metal upon the activecarbon support in the form of a salt, use may be made of a readilydecomposable compound suchas carbonyl, which can then be thermallydecomposed to yield the catalytic metal. Even when nickel and cobaltcatalysts are derived from the metal carbonyls, it is advisable tosubject the catalysts to a treatment to removecarbon monoxide which hasbeen adsorbed by the porous active carbon, e. g. to evacuation or tostripping with chemically inert gases such as nitrogen, at elevatedtemperatures between about 175 C. and about 400 C. Adsorbed carbonmonoxide may be removed from the catalyst by treatment with hydrogen at175 C. to 400 C. and hydrogen pressures of about 200 to about 2000 p. s.i. g.

At relatively low concentrations of catalytic metal on active carbon,high pressure and low temperature, the possibilities of increasing theproportion of high molecular weight tough,

resinous polyethylene in the total polymer are,

increased. At low metal concentrations (.01 to 5 weight percent) on theactive carbon, it is more desirable to pretreat the active carbon bywashing with nitric acid to minimize the ratio of acid-solublecontaminants in the active carbon to the catalytic metal.

We have found that active carbon supportednickel, under certainconditions, yields substantially greater amounts of tough, resinous highmolecular weight polymers from ethylene than cobalt/carbon catalysts. f

The particle size of the supported or unsupported metal catalysts can bevaried to suit the requirements of the reaction equipment and processflow. Thus, if a stationary bed of catalyst is desired, the catalyst maybe employed in the form of coarse fragments or pellets, e. g. ascylinders of about to inch length and 1 to inch diameter. In fixedbeds,- we may also employ 6 to 14 mesh catalysts, and the like. When itis desired to prepare a slurry of catalyst in the liquid hydrocarbonreaction medium, smaller particle size catalyst, for example, a powdercan be employed. Finer than 300 mesh powder, which can be prepared byconventional methods, e. g. by ball. milling coarse catalyst pellets orpowder, may be used.

Although we have found that ethylene can be polymerized tonormally solidpolymers at room temperature or. even lower temperatures, we prefer toemploy temperatures in the range of about C. to about 150 C., especiallytemperatures between C. and C., although temperatures up to about 250 C.or even 300 C: may be employed. Within the preferred temperature range,the normally solid ethylene polymers are in molten or semi-liquidcondition, which facilitates the removal of polymer from the catalystand appears to facilitate ethylene transfer through the polymer to thecatalyst surface. Also, the yields of solid ethylene polymers areusually at a maximum within the preferred temperature range. It will beunderstood that the selection of the best operating temperature anyspecific instance must be made in consideration of other operatingvariables, such as the catalyst activity, pressure, identity of theliquid hydrocarbon reaction medium, ethylene concentration and thespecific product distribution which is desired.

The reaction pressure should be at least about 50 pounds to obtainsatisfactory yields of solid ethylene polymers, but otherwise appears tobe limited only by the maximum pressure economically attainable in theequipment. Thus, maximum pressures in our process may be as high as15,000 pounds or 20,000 pounds or even more. However, solid ethylenepolymers can be made in satisfactory yields by the present process atrelatively low pressures, e. g. about 300, 500, 2000 or 5000 pounds,which constitutes a distinct advantage of the present process over theprocesses heretofore known to be capable of producing the same orsimilar ethylene polymerization products. In general, we prefer toemploy pressures between about 300 and 8,000 pounds. The pressures underconsideration here are total pressures in the polymerization reactionzone. However, the pressure in the reaction zone is due largely toethylene and, bearing this fact in mind, if large proportions of adiluent such as ethane are present in the feed stock, correspondinglyhigher pressures should be employed in order to obtain suitable ethylenepartial pressures in the reaction zone.

In reactors employing a fixed bed of catalyst, weight space velocitiesof ethylene can be varied between about 0.1 and about grams per hour pergram of catalyst or catalyst composite employed. In batch reactionsystems or inreaction systems wherein a slurry of catalyst, liquidhydrocarbon reaction medium and ethylene are concurrently passed througha reaction zone (such as a tower or tube), the residence time ofethylene and liquid hydrocarbon reaction medium employed will correspondtothe range of space velocities given above. Conversion of' weight spacevelocities to residence times can be efiected by calculating volume.space velocities from weight space velocities by dividing weights bydensities, and calculating the reciprocal of the volume spacevelocities.

A variety of reaction systems can be employed for the practice of thepresent process. For example, a fixed bed reactor with either downflowor upfiow of ethylene and liquid hydrocarbon reaction medium can beemployed. Parallel fixed.

bed reactors can be employed to obtain continuous operation, as in fixedbed hydrocarbon catalytic cracking units, one bed being dewaxeol and/ orregenerated while the other bed is on stream by suitable manual orautomatic time-cycle valve operations to control the flows of ethylene,liquid hydrocarbon reaction medium, catalyst dewaxing solvent andregeneration gases to each bed of catalyst.

A moving bed or slurry operation can be employed, in which a slurry ofcatalyst in the liquid hydrocarbon reaction medium is allowed to nowdownwardly through a tower or one or more tubes. Ethylene or a solutionof ethylene .in liquid. hydrocarbon reaction medium is injected into thelower portion of the tower or tubes and, optionally, at variouselevations within the tower or tubes. A slurry of catalyst and solidethylene polymers is withdrawn from the lower end of the reactor andunconverted ethylene and/or diluent gases and/or relatively low boilingpolymeriza tion products are withdrawn from the upper end of thereactor. In the moving bed operation, the solid ethylene polymers areseparated from the catalyst in a zone external to the reaction zone.Thus, the catalyst can be extracted with the liquid hydrocarbon reactionmedium or with a specially selected wax solvent in suitable equipmentand the catalyst can then be recycled to the reactor. If catalystactivity has deteriorated seriously,,the dewaxed catalyst can besubjected to a regeneration treatment prior to its recycle to thereaction zone, as willbe described hereinafter.

As will be apparentother types of reactor may also be employed. Thus,the polymerization process can be carried out batchwise in autoclavesequipped with stirring equipment, for example in autoclaves equippedwith magnetically-operated stirring devices. Likewise, stirredautoclaves can be employed even for continuous operations. An example ofan autoclave adapted for continuous operation is the so-called Stratcocontactor which has been employed to a considerable extent in thesulfuric acid-catalyzed alkylation of isoparafiins with olefins (note U.S. Patent 2,238,802 of J. A. Altshuler et al.). Still another type ofreactor which may be employed is that described in R. J. Hengstebeck, U.S. Patent 2,493,917, patented January 10, 1950. The .Hengstebeck-typereactor comprises an annular permeable catalyst bed which is partiallyimmersed in a liquid medium. The gaseous reactant is introducedcentrally of the catalytic annulus in the vapor space. This type ofreactor presents the advantage in the present instance that the bed ofcatalyst can be partially immersed in a liquid hydrocarbon reactionmedium which functions to a substantial extent also as a dewaxing orderesining solvent. The liquid medium can be drawn oif continuously orintermittently for the removal of normally solid ethylene polymerizationproducts therefrom, following which the medium can be returned to thecatalyst chamber.

In another mode of operation, catalyst, ethylene and liquid hydrocarbonreaction medium can be passed concurrently through a reaction tube orcoil, thence to a separator. This method of operation will be describedwith reference to the annexed figure.

In the annexed figure, a charging stock comprising essentially ethylene,for example ethylene concentrates as produced commercially,substantially free of catalyst poisons and reaction inhibitors, ispassed through line 10,, thence through a pump or compressor Ii, whereinit is brought to a suitable polymerization pressure, for example betweenabout 500 and 5000 p. s. i. g. The compressed ethylene is passed intoheater l2, wherein it is heated to a suitable polymerization reactiontemperature, for example, between about C. and about C. and dischargedinto a reaction coil I3 positioned within a temperature regulating bathI4 provided with valved lines l5 and 16 for the admission and removal ofa suitable temperature control iiuid. A slurry of the liquidhydrocarbon-reaction medium and fresh catalyst, for example 5 percentnickel on an activated coconut charcoal support (Burrell) which hasbeenleached with dilute nitric acid, may be charged through valved lineI! into line l0, thence into reaction coil Hi. If desired, the catalystcan be pressured directly into coil I3, at one or more points, by theemployment of conventional equipment such as lock hoppers pressured byan inert gas or, preferably, by a portion of the ethylene accaaercharging stock. Likewise, a prepared catalyst slurry in the liquidhydrocarbon reaction medium may be pumped into coil I3 at one or morepoints therein. Ethylene may likewise be injected into coil 13 at one ormore points therealong. Liquid hydrocarbon reaction medium is passedthrough line [8 into line H), thence to reaction coil IS in an amountsufiicient to constitute a distinct liquid phase in coil [3. A suitableresidence time of catalyst and ethylene may be obtained by providing asuitable length and diameter of coil l3 or by employing a plurality ofcoils in which to effect the ethylene polymerization reaction. Theprincipal advantage of employing a series of reaction coils andthermostatic baths resides in the ability to obtain individuallycontrolled temperatures and residence times in the various coils andthus to influence the extent of ethylene conversion and the productdistribution.

.Upon completion of the desired polymerization reaction, the reactionmixture is discharged through a heat exchanger l9 into separator 20,within which a desired liquid level may be maintained by the employmentof conventional liquid level control valves. Suitable temperatureswithin theseparator are between about 80 and about 150 C. Unconvertedethylene, diluent hydrocarbon gases and gasoline boiling range ethylenepolymerization products are passed from separator 20 through line 2! andpressure control valve 22, thence through valved line 23 for recycle tothe polymerization reactor or through valved line 24 into fractionator25, there to be fractioned into an ethylene recycle stream, a streamcomprising principally butenes, and gasoline. The ethylene recyclestream passes overhead through line 26, thence through valved line 21into lines 23 and H! for recycle to coil l3. If desired, part or all ofthe unconverted ethylene stream may be withdrawn from the system throughvalved line 28. A butenes fraction is withdrawn from fractionator 25through valved line 29 and a gasoline fraction through valved line 30.If desired, part or all of the butenes fraction can be combined with therecycle stream passing through line 26. When a gasoline boiling rangeliquid hydrocarbon reaction medium is employed, as in the case ofbenzene or xylenes, a substantial proportion thereof is removed with thegasoline fraction in fractionator 25. Accordingly, it may be desirableto recycle the total gasoline fraction to the polymerization reactor tofunction as the liquid hydrocarbon reaction medium or, if desired, thegasoline stream leaving fractionator 25 through valved line 30 may berefractionated to separate the desired liquid hydrocarbon reactionmedium for recycle to the polymerization reaction zone.

A mixture of catalyst, solid ethylene polymerization products and liquidhydrocarbon reaction medium separates in the lower portion of separator20, whence it is withdrawn through line 3| and recycled, totally or inpart through valved line 32, manifold 18 and line H] to reaction coilI3. Usually, however, all or part of the solidsliquid mixture withdrawnfrom the lower portion of separator 20 is passed through valved line 33into separation equipment schematically indicated at 34. A dewaxing orderesining solvent can be introduced into equipment 34 through valvedline em. The separation equipment may take the form of a centrifuge, agravity solids classifier of the Dorr type or a filter, for example afilter press or rotary filter. When a filter press or rotary filter isemployed it is desirable to introduce a filter aid, such'as adiatomaceous earth through line 35. The principal function of separationequipment 34 is to separate the liquid hydrocarbon reaction medium or,usually, a solution of relatively low molecular weight solid ethylenepolymers in the liquid hydrocarbon reaction medium from catalystcontaining adherent, relatively high molecular weight solid ethylenepolymers. The separation is usually accomplished at or about roomtemperature, or up to about 300 C.

The solution of grease-like and/ or paraflin waxlike polymers in theliquid hydrocarbon reaction medium is withdrawn from the separationequipment 34 through valved line 36 into a heat exchanger 37, whereinthe temperature of the solution is brought to a desired value for thesubsequent separation step. Thus, 31 may represent a direct or indirectheat exchanger, for example equipment in which liquefied propane ismixed with the solution of ethylene polymers in the liquid hydrocarbonreaction medium and then partially evaporated to obtain a suitablereduction in temperature. The cooled mixture is then passed through line38 into filtration equipment 39, which may take the form of a filterpress or rotary filter. A paraffin wax-like product is removed from thefiltration equipment 39 by line 49 and the liquid hydrocarbon reactionmedium containing grease-like relatively low molecular weight ethylenepolymers, optionally in admixture with a liquefied hydrocarbon dewaxingsolvent such as propane, is discharged through line 4| and heater 42into line 43, thence to an evaporator 44 which is provided with aheating coil or jacket 45. The liquid hydrocarbon reaction medium isevaporated in tower 44, whence it is removed through valved line 46 forcondensation and recycle to the polymerization process. Relatively lowmolecular weight grease-like ethylene polymerization products form amelt in the lower portion of tower 44 whence they are removed throughvalved line Catalyst containing more or less high molecular weight solidethylene polymers is removed from separation equipment 34 through line48, whence all or part thereof may be passed through valved line 49,commingled with liquid hydrocarbon reaction medium in manifold l8 andrecycled to polymerization coil l3. If desired, part or all of thecatalyst passing through line 49 can be diverted through valved line 43ainto regeneration zone 5?, whose operation will be describedhereinafter. Usually all or at least a substantial part of the contentsof line 48 are discharged through valved line 50, thence into line 5|and catalyst dewaxing or deresining equipment 52. A deresining solventis likewise introduced into zone 52 through valved line 5|.

The dewaxing or deresining solvent may be the same as or different fromthe liquid hydrocarbon reaction medium. The solvent is preferably anaromatic hydrocarbon such as benzene, toluene, a xylene, p-cymene,sec-butylbenzen and the like, although we may employ other solvents suchas ethyl benzoate, fiuorobenzene, anisole, etc. The extraction equipment52 may be of conventional design. In order to extract the tough,resinous, high molecular weight ethylene polymers which tend to betenaciously retained within the pores of the metal-charcoal catalysts,it is important to conduct the extraction operation at temperaturesbetween about the softening points and melting points of the polymers,usually temperatures within the range of about C. to about C. althoughtemperatures up to about 300 C.

may be employed. When a relatively low boiling solvent such as benzeneis employed it will be necessary to-conduct: the extraction or catalystdewaxing under suflicient pressure to maintain the solvent substantiallyinv the liquid phase at the desired extraction temperature. A solutionof waxy and. resinous ethylene polymers in the solvent is withdrawn fromthe extraction equipment 52' through valved'line 53. Essentially all thesolute can be recovered from this solution by cooling to roomtemperature or even lower temperatures, e. g. about 10 0., andfiltering. By reducing the temperature of the solution gradually,fractional crystallization may be obtained, the highest molecular weightresins being'the first to separate as solids from the solution.

A portion of the liquid hydrocarbon reaction medium may be passed intozone 52 through valved line 54 to form aslurry with the dewaxed andderesined catalyst therein, which slurry may be withdrawn through valvedline 55 for recycle through manifold 18 into the polymerization coil I3.Part or all of the dewaxed catalyst may be passed from zone52throughvalved line 56 into a regeneration zone indicatedv schematically by 57.

Regeneration of the metal-carbon catalyst may be effected by treatingthe catalyst with hydrogen-containing gases at a temperature betweenabout 175 C. and about 400 0., preferably between about 200 C. and about250 C., under suitable pressure, for example pressures up "to about 2000p, s. i. g. If desired, regeneration of the catalyst may be eifected bytreating it in zone 51 with oxidizing gases, for example a stream offlue gas containing a low concentration of free oxygen, followed byreduction of the catalyst with hydrogen to produce the active metal asabove described. The regenerating'gases may be introduced into zone 51through valved line 58 and withdrawn therefrom through valved line 59.In addition to the above described regeneration'treatments the catalystmay also be washed with nitric acid having a concentration between about15 and about 20 weight percent. at about room temperature. Theregenerated catalyst is withdrawn from zone 51 through line 60, thenceinto manifold 18 for recycle through linel into polymerization coil [3.

It should be understood that numerous en-- gineering details such asvalves, pumps; controllers, etc. have been omitted from the. annexedfigure in the interests. of simplifying the de. scription.

The above-described polymerization process can be conducted andcontrolled to produce hydrocarbon greases having a molecular weightrange of about 300 to about 750 (Menzies- Wright), which havesubstantial solubility in cold xylene fractions and a relativelyhighlyrelatively high degree of branching, the methyl ene:methyl groupratios as determined by infra- 14 red spectroscopy being in. the rangeof. about 15' to about 25, for example, 13.

The hydrocarbon greases produced .by the present invention may beemployed as a high viscosity index addition agent to lubricating oilsand; greases and may generally be employed as an impregnating wax, matchwax and for compound:- ing with other waxes and oils The grease-likeproducts are miscible with petroleum-derived paraifin waxes. The greaseand parafiin. waxlike products produced by the present invention. may besubjected to high temperature vapor phase cracking to producehighmolecular weight. monooleflns which can be polymerized. to extremelyhigh V. I. lubricating oils by treatment with Friedel-Crafts catalysts,particularly alumi!- num chloride promoted by small proportions ofhydrogen chloride. The grease-like and wax-like.- products may also besubj ected'to catalytic cracking with activated clays or silica-aluminaorsilica-magnesium type cata1ysts, optionally to-- gether withconventional charging, stocks, to. produce high octane number gasolines.Thegrease like and wax-1ike products may also be chlori'-- nated,predominantly to the stage of mono-,

chlorohydrocarbon compounds which may be chemically condensed withnaphthalene or the like in the presence of aluminum chloride to providepour point depressants for wax-containing. lubricating. oils.

The tough, resinous high molecular weight'polymers which can be producedby the above-described process are characterized by partial solubilityin boilingxylene (one atmosphere), soften-- ing points between about '70and about C.,.

melting points between. about 100 and about C.v and specific viscosities(1 sp 10 Staudinger: method) between about 10,000 and about 25,000. Thetough resinous polymersare characterized by relatively infrequentbranches in the otherwise linear molecule, the methylenezmethyl group:ratios as determined by infrared spectroscopy being between. about:20'and'about 30. The tough resinous ethylene polymers can be castor'molded into tough, thinzfil'rns or fairly rigidl thick films and maybe processedv by the-methods heretofore employed in the treatment andformulation of. the well known commercial polyethylene resins.

Thev high molecular weight resins produced by our process may be appliedto the. same or similar. uses as the commercial polyethylene resins..Even, thin films of the high molecular weight resinous products producedby the present invention are characterized by extreme chemicalresistance,

high tear strength, high tensile strength, trans-- parency and highelectrical insulating capacity. The tough resinous high molecular weightpoly-- mers can be chlorinated to a high chlorine con. tent to produceinteresting plastic materials.

The following specific examples are supplied-in the interests of clearlydelineating species of our broad process andnot for the purpose ofunduly limiting or restricting the scope of our invention. The exampleswill be presented in considerable detail to enable their reproduction bythose skilled in the art with the exercise of a minimum of independenttesting'or the exercise of independent judgment or discretion.

In the tabulated examples the cobalt-carbon and'nickel-carbon catalystswere prepared, except as otherwise indicated, by absorbing cobaltousnitrate hexahydrate andnickelous nitrate. hexahydrate, respectively, onan activated coconut charcoal (Burrell) characterized by a surface areaof about 1130 square meters. per gram, a.

pore, volume of about 0.59 cc. per gram and a pore diameter of about 21A. This activated coconut charcoal was found to contain very smallproportions of sodium, potassium, chloride, phosphate and carbonate andchemically combined oxygen. When the charcoal is covered with water theresultant aqueous solution is slightly basic, having a pH of about 9.The activated coconut charcoal was found to contain no ammonia and onlytraces of heavy metals. Prior to impregnating the coconut charcoal withcobalt or nickel nitrate it was usually leached with dilute nitric acid,employing for example, about 800 ml. of nitric acid per 500 ml. ofcharcoal. The nitric acid strength was between about 15 and about 20weight percent and it was employed at about room temperature with acontacting period of about /2 hour. Contact of the activated coconutcharcoal with dilute nitric acid results in a vigorous degassing(principally deaeration and the evolution of CO2), followed by a smalltemperature rise and after a minute or two, the evolution of N02 fumes,which stops after a few minutes. After the spontaneous evolution of N02has ceased the mixture can be heated up to about 60 C. without furtherevolution of N02. The charcoal is filtered from the spent nitric acidand dried on a hot plate. Between about 3 and about 8 weight percent ofthe activated coconut charcoal is extracted by the nitric acidtreatment. In a typical instance in which 3.8 weight percent of solidswere leached from the activated coconut charcoal by the nitric acidwash, a cation analysis of the leached solids was as follows:

K 23.70 Na 0.59 Ca ..L 6.25 Fe 0.25 P 1.66 A1 0.25 Mg 1.45 Mn being35.05 weight percent of the 3.8 weight percent total.

The cobaltous nitrate hexahydrate which was usually employed in thedeposition of cobalt on the activated carbon contained the followingimpurities (in percent by weight) Insoluble mat- Cu 0.005 ter 0.01 Fe0.006 C1 0.0008 Ni 0.008

Alkalies and earth as S04- 0.01

The nickelous nitrate hexahydrate which was usually employed in thedeposition of nickel on the activated carbon contained the followingimpurities (in percent by weight):

C1 0.0003 Co 0.03 S04 0.000 Fe 0.0004 NH: 0.05 Zn 0.003 Pb 0.0005 Earthsand al- Cu 0.0005 kalies as S04- 0.25

In the preparation of the catalysts, an aqueous solutionof the metalnitrate was brought into contact with the activated carbon support and asufficient amount of nitrate was adsorbed to yield the desired quantityof metal on the carbon. The metal nitrate on the active carbon wasthermally decomposed to yield the corresponding metal oxide, usuallyunder a reduced pressure between about 1 and about 20 mm. of mercury,absolute. The metal oxide on the active carbon was then reduced bytreatment with hydrogen at temperatures between about 250 C. and about350 C. and pressures between about 900 and' about 1500 p. s. i. g.

In examples tabulated herein, operations were conducted in someinstances in batch reactors and in other instances, in a continuous flowreaction system. The batch reactors employed were hydrogenation rockingbombs of conventional design having an empty volume of about 183 ml. Inthe batch reactors, granular catalysts of about 6 to14 mesh size wereemployed. The usual procedure in making the batch runs was to force aliquid hydrocarbon reaction medium into the reactor containing thecatalyst, thereafter withdrawing sufficient hydrocarbon to provide acalculated vol-- appearance at the end of the reaction, due to thepresence therein of suspended, finely-divided ethylene polymer of highmolecular weight.

As indicated in the tables, in some examples a slurry of powderedcatalyst (300 or more mesh per inch) in the liquid hydrocarbon reactionmedium was employed in some of the batch reactor runs. 7

The usual reaction period in the batch reactors varied between about 2and about 4 hours, the runs ordinarily being terminated because of asubstantially decreased pressure drop as compared with the initialpressure drop.

The flow reactor indicated in certain of the tabulated examples was avertical steel tube having internal diameter of 1.1 inches and volume of450 ml. packed with a fixed bed of 6-14 mesh catalyst. The reaction tubecontained a central well containing three thermocouples, viz., one atthe upper end, one at the middle and one at the lower end of the well.One-fourth inch copper tubing was wound about the reaction tube and airor water was circulated therethrough for temperature control in thereaction tube. Two electrical resistance coils were wound over thecopper coils to provide heat. The entire assembly was suitably laggedwith insulating material. In all the flow runs operation wassatisfactory. The polyethylene product was extruded from the reactor asa white slurry in the liquid reaction medium and was easily collected inthe products receiver. The flow runs were usually terminated not becauseof substantial decrease in catalyst activity but because usuallysufficient product had been obtained at the termination time to indicatethe success or failure of a run and to pro.-'

vide sufiicient material for analytical work.

The specific viscosity values given in the tables (7131x10 were obtainedby employing the Staudinger formula (Z. Phys. Chem. 171, 129 (1934)),using 0.125 gram of polyethylene per 100 ml. of boiling xylene at C. forviscosity measurements.

Referring now to Table 1, run 1 relates a test in which a nitricacid-washed, activated coconut charcoal which had been treated withhydrogen was employed in order to test its catalytic activity forethylene polymerization. It will be noted that activated charcoal aloneevidenced no catalytic activity, since no solid ethylene poly- 17 merswere produced. Run 2 shows that even unextended or unsupported cobaltwill catalyze the production of solid wax-like and grease-like ethylenepolymers in the presence of benzene. In

18 temperature. Runs 11 and 12 were conducted at 121C. which is asatisfactory temperature for operations with the nickel catalyst in thepresence of benzene as the liquid hydrocarbon reaction addition to the0.1 g. of wax, 0.2 g. of grease was medium. It will be noted that ineach instance, also produced in run 2. However, as will appearsubstantial yields of relatively high molecular hereinafter, thecatalytic activity of the unsupweight ethylene polymers were produced.By ported or unextended cobalt or nickel catalysts is comparison, in run13 the yield of solid ethylene of a low order relative to the activityof the polymer was considerably reduced and the averactivatedcarbon-supported metals. in age molecular weight thereof also wassomewhat A comparison of runs 3 and 4 indicates the lower. relativetolerance of the process of the present Some insight on the effects ofpressure can be invention for oxygen in the charging stock in gained bya comparison of runs 14, and 16. In amounts such as are normallyencountered in un 1 in w c e pressure W s O y 600 commercial cylinderethylene. In run 3 the 15 sa, 3 w i t e t of t y n charge oxygenconcentration in ethylene was 950 p. p. m., was Converted, whereas inrun 15 at a pressure of whereas i run/1 11-, was 3 p 11-, ill b 2200 p.s. i. g. 93 weight percent of the ethylene noted that the difference inthe yield of solid cha e as converted. However, the product disethylenepolymers was not substantial. Although tribut-ions in runs 14 and 15were substantially oxygen did not apparently interfere in thepolyidentical and the grease like products had similar merizationreaction, it will cumulatively convert ec la weights. It will be notedfrom r n 14 the reduced metal catalyst to metal oxide which and 15, thateven at relatively low pressures in is catalytically inactive. thepresence of the Xylene reaction medium the Table 1 Catalyst Solvent TypeProduct-Wax and resins Run T emp Pressure, Time, of Remarks No.Description Grams Type M1. 0. p'silgl mm reactor Grams 1-1000 1 HNo-treated 00- 84 Benzene 125 127 1,060-360 85 Bat h. None Test orcharcoal conut charcoal alone. pretreated with i 2 lfifj gg lg g lt 90do 50 121 ,040-900 345 .d0 0.1 No catalyst support,

metal-no char- 3.. ma cobalt on 123 do. 125 126 1,020-500 50 do. 2.3116-17 70-75 1,180 0.5 g of additional HN OS-treated resin was extractedcoconut charwith sec.butylbencoal (Ozin C2H4, zone.

4.". 1o 7 o'o ta i t 'on 133 do..-. 125 127 1, 020700 130 do 3.5 107-8so 1, 500

HNOrtreated coconut charcoal (0: in 02114,

3 p. p. m.).

Table 2 presents data obtained in studies with product distribution wasWeighted almost entirely activated carbon-supported nickel catalysts. Ain favor of the production of normally solid ethylcomparison of runs 5and 6 indicates that lowerone polymers, little or no gasoline beingproduced. ing the concentration of the nickel in the reactor Similarproduct distributions have been observed somewhat reduces the rate ofsolids production inflow operations at 300 p. s. i. g. (Table 5). Runfrom ethylene, as well as the ethylene conversion 16 was a batchreaction experiment in which the in a given period. In run 5, 28 weightpercent ethylene pressure was allowed to decreaseduring of the ethylenecharge was converted Whereas in the reaction period from an initialvalue of 6000 run 6 only 9 weight percent was converted. How- 1 S- i goa terminal pressure O 0 1 s. i. ever, it will be noted that the productdistribu- It w l be noted h t a solid p y r havin a tion was notsubstantially difierent in runs 5 and Specific Vis osity f about 15,000Was produced- 6. The molecular weight of the grease producedrha-clionhtion 0f the Solid p y y eXylene e in run 5 was 4&0(lvlenzies-wright method). The traction showed it to consist ofapproximately 25 melting point of the wax produced in run 5 was percentof a wax and '75 percent of white, resinous 117413" C. e y hyl g oupratiO of Polymer having a specific viscosity which is probthe w productv d r m un 5 w s 3. ably in excess of 18,000 but which could not be asdetermined by infrared spectroscopy. 0 precisely determined because thehigh molecular f thevyleld OI Sohd polymer per a of mckel weight of theresin greatly reduced its solubility n the catalyst was actuallysubstantially higher even in boiling xylezm ii l nltiiffifinit and 8indicates that A wax'like polyme having Specific Viswsity in the rangestudied, the yields of solid products 5 (X105) of 2400 was producfd ythe polymenza; were roughly proportional to the catalyst concene ofethylene at 50 the presence tration. A product of Very high SpecificViscosity 7.0% n ckel-charcoal catalyst in a. batch reactor, wasproduced in run 9, in which a wood charcoal employmg 100 m1? of Xylenesfractlon as the suppgrt was used, action medium at 121 C. for 120minutes. Ethyl-.

som i di ti of th efiect of the operating one was recharged atintervals. A cumulative temperature in the present process can be gainedpressure p of 55 pof ethylene 5 by a comparison of runs 10, 11, 12 and13. It will Served during the be' noted that in run 10, somepolymerization of A Compa 0f t e effects of the ethylene ethylene toyield normally solid products (average concentration in the liquidhydrocarbon reaction molecular weight, 950) was obtained even at roommedium, which was a commercial xylenes frac tion, is had in runs 17 and15. With the low ethylene concentration, (run substantially completeethylene conversion was obtained (93%), dropping rather steeply at thehigher ethylene concentration in the liquid hydrocarbon reaction mediumto a value of 36% ethylene conversion. However, the productdistributions at low and high ethylene concentrations were notsubstantially different. A high concentration of the hydrocarbonreaction medium in the reaction zone is desirable since it usually aidsin removing solid polymer from the catalyst; conversely, at highethylene concentrations in the hydrocarbon reaction medium the reactionproduct may in some instances consist essentially of a dispersion of theliquid hydrocarbon reaction medium in a preponderant proportion of solidpolyethylenes.

Run 18 was conducted with regenerated catalyst obtained by extraction ofsolid polyethylenes from the catalyst used in run 17, followed by hightemperature treatment with hydrogen. While the extent of ethyleneconversion was somewhat lower when the regenerated catalyst wasemployed,

substantial solid polyethylene yields were nevertheless obtained.

The efiects of various supports for the nickel catalyst can be discernedby comparing runs 9 and 19-23, inclusive.

It will be noted from run 19 wherein silica gel was employed as asupport for nickel that only bare evidence of reaction was obtained, andthis in spite of the fact that 115 ml. (96 grams) of catalyst wereemployed rather than the usual quantity of about grams. In run 20, acommercial nickel-kieselguhr hydrogenation catalyst was reduced withhydrogen and tested; no polyethylene was formed. The catalyst had beentreated before use with hydrogen at 400 C. and atmospheric pressure for5 hours. It appears from a comparison of runs 19 and 20 with other runsin which the catalyst was supported upon activated carbon that there issome specific inter action between the metal and-the carbon to produce acatalyst having an efficacy far greater than that of either componentalone. As has been shown, the use of unextended metal leads only torelatively low yields of solid polymer (run 2) and the use of activatedcarbon alone to no yields of solid polymer whatsoever (run 1').

The catalyst in run 9 was nickel supported on "a powdered nitricacid-leached wood charcoal having a surface area of 745 square metersper gram, pore volume of 0.57 cc. per gram and pore diameter of 30.6 A,before impregnation with nickel nitrate; It will be noted that althoughthe yield of polymer was rather low in run 9, the molecular weight wasVery high, as the product was a tough, pliable film, rather than awax-like or grease-like material.

Run 21 illustrates the fact that leaching an activated carbon withhydrochloric acid is extremely detrimental to catalyst activity. Thiswill be especially evident by comparison with run 22 in which noleaching step whatever was employed and the yield of solid ethylenepolymer was consequently about 50 times as great and the molecularweight was substantially greater. In run 23, the coconut charcoalsupport was twice leached by immersion in dilute nitric acid. Thecatalyst made by impregnation of this charcoal was very active, asindicated by the tabulated data. Dilute nitric acid leaching ofactivated carbon supports is probably more efiective at lowconcentrations of nickel or cobalt, since in such cases the ratio ofimpurities extracted by the 20 leaching operation to the metal arenaturally greater.

In run 24 the feed stock was propy rather than ethylene. The propyleneconversion was extremely low, being only 3 weight percent based on feed,and only a low molecular weight jelly-like product was produced. Thecontrasting behavior of ethylene in the present polymerization processis quite striking.

Run 25 illustrates the inhibiting effect of even relatively smallproportions of acetylene in the polymerization of ethylene by thepresent process. The predominant solid product was a grease. Onepossible explanation relates the deleterious efiect of acetylene toformation of acetylides on the catalyst. Under otherwise similaroperating conditions but in the absence of acetylene the yield of solidethylene polymer would have been of the order of 60 grams.

We have observed striking and unexpected effects which are attributableto the liquid hydrocarbon reaction medium in the present reaction withnickel catalysts. A comparison of the efiects of various liquidhydrocarbon reaction media is afiorded in runs 12 and 26 to 35,inclusive, in which the sole substantial variable was the identity ofthe liquid hydrocarbon reaction medium. In run 12, the employment ofbenzene yielded 9.? grams of polymer having a specific viscosity of3000. In run 26, the use of a mixture of xylenes (boiling range 137.7 to138.6 C.) led to a markedly higher polymer yield and much of the polymerproduced was of substantiall higher molecular weight.

The employment of ethylbenzene (run 27) produced an amount of polymersimilar to that .ob-.

tained With benzene but of muchhigher specific viscosity. A mixture ofxylenes and p-cymene (run 28) yielded results similar to those obtainedwith xylenes alone. The use of mesitylene (run 29) led to a good yieldof tough, pliable high specific viscosity polymer. Second-stageextraction of the used catalyst from the mesitylene run with boilingxylenes yielded a tough polymer of 17,600 specific viscosity. It will benoted that the use of alkylbenzenes, particularly methylbenzenes,produces high yields of polymers of unexpectedly high average specificviscosities, as compared with the results obtained y using benzene.

A surprisingly effective reaction medium was n-octane (run 30), althoughit was less effective for the production of high specific viscosityethylene polymers than the alkylbenzenes. Isooctane (run 31) wassubstantially less efiective than noctane from both the product yieldand specific viscosity standpoints.

The naphthenes methylcyclohexane (run 32) and decalin (33) did not proveto be as good as xylenes. Tetralin, which may be regarded as analkylbenzene (run 34), led to the production of polymers in yieldscomparable to those obtained by the use of xylenes but of even higherspecific viscosity.

Aliphatic olefins or olefin polymers are not useful reaction media forthe purposes of the present process since they lead to very low or onlytrace yields of ethylene polymers having molecular weights of at least300. Thus in run 35, the emquality were both far inferior to thoseobtained with the other reaction media, such as xylenes,

mesitylene, n-octane, etc. Similar disappointing results have beenobtained upon the use of hoctene and tetradecene.

Remarks =1.92X10- (second order N reaction). Total product was a grease.

First product was benzene soluble. Second product was obtained by 8soxhlet extractions of the catalyst with refluxing xylene. Third productwas obtained by a 9th extraction of the catalyst with refluxing xylene.

2,692,261 26 In Table 3 are presented data illustrating the effects ofcobalt-charcoal catalysts. It will be noted from run 36 that the cobaltcatalyzed poly- .merization of ethylene gave good results even thoughthe run was terminated because of the rupture of a safety disc. Thespace velocity (both ethylene and benzene) was 0.3 g./hr./g. catalystand 45 weight percent of the feed stock was converted. In run 37, inwhich the feed was pro- 10 pylene, the product was largely propylenedimer.

A comparison of vapor phase ethylene polymerization and ethyl nepolymerization in the presence of a liquid hydrocarbon (ben- Trace zcne)medium is presented in Table 4, which also affords a comparison ofnickel and cobalt catalysts. It will be noted from the data Nonepresented in Table 4 that the presence of a liquid hydrocarbon reactionmedium favorably affected the ethylene polymerization reaction in thedirection of producing increased yields of normally solid polymers ofethylene. The presence of a Product distribution, weight percent SolidGrease liquid hydrocarbon reaction medium was shown substantially toincrease the proportion of solid ethylene polymers in the total productsproduced by ethylene polymerization. Specifically, with the cobaltcatalysts, the use of benzene as the re- Grease action medium (run 39)reduced the yield of gasoline boiling range products to about 53 percentfrom the value of about 80 percent obtained in the vapor phase operation(run 38) and the yield of grease-like polymers was more than doubled.

Product With the nickel catalyst the results were even more striking,since vapor phase operation (run 40) yielded only a grease-like product,whereas in the presence of benzene (run 23) half the product wasWax-like material of 3400-4900 specific viscosity (X10 It will be notedthat nickel is Wax and resins Grams O- mpXlo M. W. Grams M. w.

sic 103-4 5.2 117-8 0.3 121-2 superior to cobalt for the production ofhigh molecular weight polymers.

Even more striking product distribution-s weighted almost exclusivelytowards high molecular weight polymers to the substantial exclusion Typeof reacof gasoline boiling range products will be apparent from theillustrative continuous flow operations with nickel-charcoal catalystsset forth in Table 5.

In this operation, xylene was circulated downfiow over a 5%nickel-on-charcoal catalyst at such a ethylene polymer was produced andcollected in five portions. Similar operations conducted at an ethylenepressure of 900 p. s. i. g. had little or no effect on the specificviscosity of the products (average), but the solid products constitutedSolvent Type between about 50 and 90 percent of the total.

TABLE 4.--C 77Zp17'i80n of ethylene polymerization in vapor phase andwith liquid hydrocarbon reaction medium Grams 103 None...

104 Benzene 125 96 None-...

Catalyst Description treated coconut charcoal.

coconut charcoal (doubly HNO3-treated). 5% nickel on HNOa-treatcdcoconut charcoal.

Table 5 Ex- 7 trac- Period 1 2 3 4 5 catalyst Ethylene, p. s. i. g 300300 300 300 300 S. V. (v01. Xylene/Vc./hr.). 1. 7 l. 7 2. 2 3. 3 l, 8Temperature, O 124 124 124 124 124 Grams of product:

Grease 6.1 4. 8 4. 8 1.2 1, 1 7 SOIId. 6. 4 s. c 2. 0 1.1 1. 4 'locaL.l2. 5 7. 8 6. 8 2. 3 2. 5 1w l0 (solid). 7,100 9, 500 10, 000 11,100 7,600 Molecular weight (grease). 439 598 367 588 589 Weight percentproducts:

Grease 49 62 52 44 33 clid 51 38 29 48 56 67 Run 38 5% cobalt on doublyHNOs- 39--. 5% cobalt on HNOa-treatecl 2s... g i g gag fgfg ggg 97Benzene. 125 126 About 1,200. as ...do

27 Data obtained in the attempted polymerization of ethylene withvarious catalysts other than nickel and cobalt are presented in Table 6.

3. The process of claim 2 which comprises the additional step ofextracting the catalyst with a.

Table 6 Catalyst Solvent Run. Ternpn, Pressure, Duration, Type of No. C.p. s. i. g. minutes reactor Description Grains Type Ml.

ironrlilNrtreated coconut charcoal- 115.5 Benzenef. 125 121 1,100- 800130 Batch.

. 5% copperHNa.treated coconut charcoal. 95 '12l 1', 060-1, 000- Y 240Do.

5% zinc'oxideHNO3-treated coconut charcoal. 95 121 LOGO-1,000 120 Do.

1% Pd-HNOrtreated' coconutcharcoal 92 121 1,060-1, 020 150 I Do.

It was found in run ll that although iron was not completely inactive asa catalyst, since. it yielded of the order of 0.1 weight percent ofsolid ethylene polymer, the iron catalystwasnevertheless farinferior tocobalt-carbon and nickelcarbon catalysts. The polymer obtained in run4'1 was of relatively low molecular weight.

In run 42, in which copper supported on nitric acid-washed coconutcharcoal was employed as the catalyst, essentially negative results wereobtained. Qnly a trace of polymer whichwas too small to weight readilyappeared as a light scum on the surface of the beaker.

In run 43 a zinc oxide-charcoal catalyst was employed. The zinc oxideproduced by the decomposition of zinc nitrate could not be reduced withhydrogen. catalyst gave only a trace of solid ethylene polymer;

In run 44 a palladium charcoal catalyst was employed and found to giveresults similar to the copper-charcoal catalyst. Although palladium,cobalt and nickel have the common property of being, good hydrogenationcatalysts it will be apparent from the data herein presented that theyare by no means functional equivalents for the polymerization ofethylene.

Having thus described our invention, what we claim is:

l. A process which comprises contacting ethylene with about 50 percentby weight thereof of a catalyst consisting essentially of 5 percentnickel deposited upon a nitric acid-washed activated coconut charcoalhaving a surface area of about 1150 square meters per gram in thepresence of a mixture of xylenes in the amount of about 3 /2 grams pergram. of ethylene charged at a temperature of about 120 C. and, apressure of about 1000 p. s. i. g., and; thereafter separating a tough.resinous. polyethylene. a solution of 0.125 gram of which dissolved in100 ml. of Xylene. at 85 0.. having a specific viscosity (1]sp .10. of.about 18,500 asa product of the reaction.

2. A process for polymerizing ethylene. which comprises contactingethylene with a catalyst comprising essentially an activatedcarbon-supported metal selected from the class consisting of nickel,cobalt and mixtures of cobalt and nickel inthe presence of a liquidhydrocarbon reaction medium selected from the class consisting ofalkanes having more than 3 carbon atoms per molecule, cycloalkanesandaromatic hydrocarbons, the. proportion of said medium being at leastabout weight percent of the weight of ethylene and said medium,effecting. said: con.-

tacting under suitable polymerization conditions including a temperatureselected within the range of. about 10 C. to. about 300 C. and apressure of at least about 50 p. s. i. g., and separating poly--merization. products comprising a substantial proportion of an ethylenepolymer having, a molecular weight of at least about 300.

solvent, thereby recovering a normally solid polymer of ethylene fromsaid catalyst.

4. The process of claim 2 wherein said. polymerization temperature isbetween about C. and C. I

5. The process of claim 2 wherein said polymerization temperature isbetween about 100 C. and about 150 C. and the polymerization pressure isbetween about 300 and about 8000 p. s. i. g.

6. The process of claim 2- wherein saidactivated carbon is a charcoalderived from a cellulosic material, said charcoal having a surface areabetween about 700 and about 1200 square meters per gram.

'2. The process of claim 2 wherein said activated carbon is an activatedcoconut charcoal.

8. A process for polymerizing ethylene which comprises contactingethylene with a catalyst comprising essentially an activated coconutcharcoal-supported nickel in the presence of a liquid hydrocarbonreaction medium selected from the class consisting of alkanes havingmore than 3 carbon. atoms per molecule,. cycloalkanes and aromatichydrocarbons, the proportion of said medium being at least about 10weight percent of the weight of ethylene and said medium, eiiectin saidcontacting under suitable polymerization conditions including atemperature selected within the range of about 10 C. to ab0ut300 C. anda pressure of at least about 530 p. at g., and separating polymerizationproducts comprising a substantial proportion of normally solidpolyethylenes.

9. The process of claim 8 wherein said. polymerization temperature is.between about 100 C. and about 150 C.

10. The process of claim 8 wherein said liquid hydrocarbon reactionmedium is an aromatic hydrocarbon.

11. The process of claim 8 wherein said liquid aromatic hydrocarbonreaction medium. comprises methylbcnzenes.

12. The process of claim 8- wherein said liquid hydrocarbon reactionmedium is a. saturated hydrocarbon having more than 3 carbon atoms permolecule.

29 conditions including a temperature selected within the range of about10 C. to about 300 C. and a pressure of at least about 50 p. s. i. g.,and separating polymerization products comprising a substantialproportion of normally solid polyethylenes.

15. The process of claim 14 wherein the polymerization temperature isbetween about 100 C. and about 150 C.

16. A process for polymerizing ethylene predominantly to normally solidpolymers, which process comprises contacting ethylene and a xylene, theproportion of said Xylene being at least about 10 weight percent of theweight of said ethylene and said xylene, with a catalyst comprisingessentially activated carbon-supported nickel at a. temperature betweenabout 100 C.

and about C. and a pressure between about 500 and. about 5000 p. s. i.g., and separating normally solid ethylene polymerization productshaving an average molecular weight of at least about 300 as a reactionproduct.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,181,640 Deanesly Nov. 28, 1939 2,231,231 Subkow Feb. 11,1941 2,259,961 Myddleton Oct. 21, 1941 2,457,556 Heinemann Dec. 28, 19482,460,303 McAllister Feb. 1, 1949 2,500,056 Barr Mar. '7, 1950

2. A PROCESS FOR POLYMERIZING ETHYLENE WHICH COMPRISES CONTACTINGETHYLENE WITH A CATALYST COMPRISING ESSENTIALLY AN ACTIVATEDCARBON-SUPPORTED METAL SELECTED FROM THE CLASS CONSISTING OF NICKEL,COBALT AND MIXTURES OF COBALT AND NICKEL IN THE PRESENCE OF A LIQUIDHYDROCARBON REACTION MEDIUM SELECTED FROM THE CLASS CONSISTING OFALKANES HAVING MORE THAN 3 CARBON ATOMS PER MOLECULE, CYCLOALKANES ANDARCOMATIC HYDROCARBONS, THE PROPORATION, OF SAID MEDIUM BEING AT LEASTABOUT 10 WEIGHT OF THE WEIGHT OF ETHYLENE AND ABOUT SAID MEDIUM,EFFECTING SAID CONTACTING UNDER SUITABLE POLYMERIZATION CONDITIONSINCLUDING A TEMPERATURE SELECTED WITHIN THE RANGE OF ABOUT 10* C. TOABOUT 300* C. AND A PRESSURE OF AT LEAST ABOUT 50 P. S. I. G., ANDSEPARATING POLYMERIZATION PRODUCTS COMPRISING A SUBSTANTIAL PROPORATIONOF AN ETHYLENE POLYMER HAVING A MOLECULAR WEIGHT OF AT LEAST ABOUT 300.